With the increasing expansion of digital technologies in global education systems, the need for a valid and reliable tool to assess the digital maturity of schools is more critical than ever. Despite the existence of numerous international models, the lack of a comprehensive model tailored to the conditions of Iran's education system is a major challenge. The main purpose of this study is to design and validate a comprehensive model for assessing the digital maturity of Iranian schools, based on global standards while being adapted to the country's local context. The primary research question is: Does the designed five-dimensional model for assessing school digital maturity have adequate validity and reliability? This study was conducted using a mixed-methods approach with an instrument development design. In the qualitative phase, the initial model was designed after a systematic literature review and interviews with 15 experts. In the quantitative phase, a sample of 450 schools from eight provinces was selected using multi-stage cluster sampling. The data collection instrument was a 24-item questionnaire designed across five dimensions: Management and Leadership, Technological Infrastructure, Digital Skills, Digital Educational Content, and Evaluation and Monitoring. The results of the confirmatory factor analysis indicated that the five-dimensional model had good fit indices (CFI = 0.956, TLI = 0.943, RMSEA = 0.067). Cronbach's alpha reliability coefficients for the five dimensions ranged from 0.808 to 0.882. The mean total score for school digital maturity was 2.88 out of 5, indicating a moderate level of digital maturity. Multiple regression analysis showed that school ownership type and the number of students were significantly correlated with the digital maturity score (p < 0.05). The designed model is a valid and reliable tool for assessing the digital maturity of Iranian schools. This model can serve as a basis for developing educational technology policies and strategic planning in the Ministry of Education. Furthermore, the results highlight the need for greater attention to developing the digital skills of educational staff and improving schools' technological infrastructure.